The invention relates chiefly to a device, for example, to one of the probe type, for penetrating and advancing into a mass of pulverulent or heavy material, typically grains, seeds or sand.
The device of the present invention can penetrate into and travel in the mass of pulverulent material, that is, for example, in a pile, a geological formation, a ship's hold or a silo or any other storage unit.
It is known on the one hand to produce a percussion apparatus for penetrating into the interior of a solid, for example, percussion drills that make it possible to drill a hole into concrete, or the earth torpedoes, which are described in French Patent 72 51742 published under number 2 161732, which enable holes to be bored in the soil.
The use of percussion devices for penetrating or advancing in pulverulent materials has never been envisaged. Furthermore, devices of the known type do not permit such use to the extent that, in a pulverulent material such as grain, the resistance to advancement comes chiefly from friction on the sides of the device. In solids, however, the resistance to advancement comes mainly from the difficulty in making a hole. The presence of the hole diminishes the pressure exerted on the sides of the apparatus. Therefore, in the experiments performed in the development of the invention, apparatuses of the known type, which concentrate 80% of their energy at the head, ceased to advance into the interior of a mass of grain at the end of a few meters. The body of the earth torpedo was immobile while the head was vibrating without producing any progress. Moreover, the applicant Company has discovered that probes having too little friction in proportion to the pulverulent material, do not succeed in advancing. The value f.sub.i of the friction of the hull of the probe, and of any guiding means rigidly attached to the hull, must be greater than the minimum value f at which the recoil of the striking piston produces a recoil of the probe. Of course, the value f.sub.i of the friction must be less than the maximum F at which the impact of the striking piston on the striking zone no longer causes the probe to advance. The user determines the optimum value of the friction taking into account the mass and the natural frequency of the probe, as well as the amount of motion delivered by the driving means to the striking piston. Tests permit optimizing the friction value, doing so for various loads pulled or pushed. The value f.sub.i can be modified, particularly increased, by the addition of guiding means fixedly attached to the hull of the probe. The value f.sub.i of the friction is substantially proportional to the surface area the probe and the added guiding means. So, to increase the value of f.sub.i, it is also possible to add a long guiding tube of small diameter or a shorter guiding tube of greater diameter. The choice of the guiding elements to be added is determined by the geometry of the container of the pulverulent material to be explored, or by the treatments to be performed within the said pulverulent material.
There exists no known method for penetrating into the interior of a pulverulent mass of ore, sand or grains.
The case of grain is particularly important. To inspect or effectively and lastingly protect cereal grains against pests it is necessary to be able to penetrate into the mass. The protection of the world's cereal reserves is one of the major economic objectives of our time. Destroying pests makes it possible to feed people.